Causes

Acromegaly occurs when the pituitary gland produces too much growth hormone (GH) over a long period of time.

The pituitary gland is a small gland at the base of your brain, behind the bridge of your nose. It produces GH and a number of other hormones. GH plays an important role in managing your physical growth.

When the pituitary gland releases GH into your bloodstream, it triggers your liver to produce a hormone called insulin-like growth factor-1 (IGF-1) — sometimes also called insulin-like growth factor-I, or IGF-I. IGF-1 is what causes your bones and other tissues to grow. Too much GH leads to too much IGF-1, which can cause acromegaly signs, symptoms and complications.

In adults, a tumor is the most common cause of too much GH production:

• Pituitary tumors. Most acromegaly cases are caused by a noncancerous (benign) tumor (adenoma) of the pituitary gland. The tumor produces excessive amounts of growth hormone, causing many of the signs and symptoms of acromegaly. Some of the symptoms of acromegaly, such as headaches and impaired vision, are due to the tumor pressing on nearby brain tissues.
• Nonpituitary tumors. In a few people with acromegaly, tumors in other parts of the body, such as the lungs or pancreas, cause the disorder. Sometimes, these tumors secrete GH. In other cases, the tumors produce a hormone called growth hormone-releasing hormone (GH-RH), which signals the pituitary gland to make more GH.